"ISTPs are masterful at emotionlessly analyzing complex systems and introducing change to improve productivity and efficiency. Definitely.
The ISTP relies on first-hand experience when forming opinions and solutions and excel when they are in situations that are physically and mentally demanding, especially when the situations are of interest to them. For this reason, they can be closet "daredevils" who involve themselves with fast-moving and/or risky activities, recreational sports and careers. Yes.
ISTPs are very balanced in movement and emotion, easily adapting to any environment, which makes them excellent in a crisis situations. Yeah, healthy ones anyway.
They are normally optimistic (without being sappy) and let few things scare them. Yes.
ISTPs are full of good cheer, loyal to their equals, uncomplicated in their desires, generous, trusting and receptive people who want no part in confining commitments. I've heard this phrase somewhere. Sure, though.
They rarely show weakness or allow petty feelings control their thought processes. They don’t need compliments or affirmation from others to be fulfilled - in fact, they are slightly disgusted when people need that kind of emotional crutch." Eh, somewhat. Nobody's fully robotic.
Pretty brief description, but seems fairly accurate.